Soft Shell Crab Scylla olivacea (Herbst, 1796) Production Using Different Types of Feed

Abstract

105-day feeding experiment was conducted at the brackishwater pond of a private operator in Sitio Iringan Brgy. Palsabangon, Pagbilao, Quezon from November 2017 to April 2018 to demonstrate soft-shell production of crab using three different types of feed. Three hundred (60-100 g) Scylla olivacea were used in the study. During the experiment, treatments used were trash fish (Treatment I), coconut meat (Treatment II), and shellfish (Treatment III). At the end of the study, S. olivacea fed with shellfish (Treatment III) obtained the highest number of molted crabs with mean value of 47.6 or 95% while trash fish (Treatment I) obtained the least number with mean value of 45 or 90%. Highest mortality was observed in trash fish (Treatment I) with mean value of 4.5 or 9% while least mortality was noted in coconut meat (Treatment II) with mean value of 2 or 4%. On the other hand, few numbers of escaped crab were noticed in the study. The highest weight gain was observed most in trash fish (Treatment I) among the three treatments with mean weight gain of 27.52 g while the least was coconut meat (Treatment II) with mean weight gain of 22.86 g. Likewise, highest carapace length gain was observed in trash fish (Treatment I) and shellfish (Treatment III) with mean length gain of 0.69 cm while least length gain was noticed in coconut meat (Treatment II) with mean length gain of 0.675 cm. Also, highest carapace width gain was seen in trash fish (Treatment I). Feeding with trash fish also had the shortest average number of days to molting (<30 d) as compared with other treatments. However, ANOVA revealed no differences regarding number of moltings, weight gain, carapace length and width gain, and survivorship among the different treatments. Meanwhile, water parameters changed as salinity and turbidity decreased from November 2017 to January 2018 and increased from February to April 2018 which was not during the typhoon season. Weather condition affect the experiment process as it caused a lot of mortality during rainy days specifically within the typhoon period. In terms of profitability, coconut is 40% cheaper than trash fish and shell fish. In line with this, Treatment 2 had the highest net income which was Php 1,806.00 and rate of return which was 51%. On the other hand, Treatment 1 had the lowest net income of Php 1,243.00 and with a 27.26% rate of return.